The present invention relates to a refuging system for emergency of a transfer feeder provided for a transfer process.
A transfer press is equipped with a transfer feeder, and in the current technology of this art field, there are provided transfer feeders generally of two types, one being a cam drive type in which a transfer bar is driven in a two- or three-dimensional direction by a driving power from a driving source of a press body, and the other one being a servo-motor drive type in which the transfer bar is driven in a two- or three-dimensional direction by a servo-motor driven and rotated in synchronism with the operation of the press body. In the above two types, the servo-motor drive type can change a feed stroke and a lift stroke optionally, and accordingly, in recent years, the servo-motor drive type has been widely utilized.
When the servo-motor drive type transfer feeder is utilized, in a case where an abnormal condition is caused to the servo system and the transfer feeder is run away, it is necessary to urgently stop the operation of the transfer feeder or to refuge the same before transfer bars or attachments such as fingers secured to the transfer bars interfere with a slide or mold of a press body. Apparatus for preventing such interference of the transfer bars or attachments with the slide or mold are disclosed, for example, in the Japanese Patent Laid-open Publication No. HEI 1-313117. Japanese Patent Laid-open Publication No. HEI 3-360824. Japanese Patent Laid-open Publication No. HEI 5-131231, and Japanese Utility Model Laid-open Publication No. HEI 4-83431. Since the apparatus disclosed in these prior art documents all utilize the servo systems to control the refuging means, such interference as mentioned above cannot be avoided when the servo system is out of order, thus being inconvenient.
FIG. 1 shows an arrangement of a conventional servo control system, in which only single dimensional direction control is described, of a transfer feeder adopting the servo-motor drive type system described above. With reference to the arrangement of FIG. 1, reference numeral 1 denotes an NC controller for controlling positions of transfer bars of a transfer feeder 6 in synchronism with the operation of a press body, not shown. Positional information of a slide and a mold of the press body are detected through a press encoder 12 for detecting an angular position of a crank connected to the slide and the mold, and the movement of the transfer bar of the transfer feeder 6 to a predetermined position is performed and controlled in accordance with the thus detected positional information.
One motor of the transfer feeder 6 is driven by a servo amplifier 2 which supplies an electric current to the motor under control, and the servo amplifier 2 is driven by an electric drive source 3 which supplies a direct current to the servo amplifier 2.
Reference numeral 4 denotes an brake power source for urgently stopping a servo motor 7 in a case where an abnormal condition is caused to the servo amplifier 2 or the NC controller 1. The brake power source 4 supplies a direct current to the servo motor 7 for braking it at the occurrence of the abnormal condition.
Reference numeral 5 denotes a selector composed of a hard logic (logic circuit) which is switchable in accordance with the factors of the abnormality of the servo amplifier 2 or NC controller 1. The selector 5 usually selects the output (U. V. W) of the servo amplifier 2 and detects the output of the brake power source 4 at an occurrence of the abnormal condition to thereby supply the direct current to the servo motor 7 to brake the same. The servo motor 7 is a motor for driving the transfer feeder 6 in a certain dimensional direction, and therefore, an induction type servo motor is usually utilized as the servo motor 7.
The rotational speed of the servo motor 7 is detected by a sensor 8 and the rotational speed of the servo motor 7 detected by the sensor 8 is fed back to the servo amplifier 2.
The rotational angle position of the servo motor 7 is detected by a position incremental encoder 9 and then fed back to the NC controller 1.
Reference numeral 10 denotes an I/O module and reference numeral 11 denotes a sequencer. The sequencer 11 serves to exchange the information with the NC controller 1 via the I/O module, and for example, serves to set the motion of the transfer feeder 6 and monitor the conditions of the NC controller 1 and the servo amplifier 2.
The conventional servo control system of the structure described above will operate at the occurrence of the abnormal condition in the following manner.
The following factors will be mentioned as abnormal condition occurrence factors of the servo control system.
a. Generation of an abnormal signal from the servo amplifier 2. PA1 b. Generation of a deviation abnormal signal from the NC controller 1 (signal representing a fact that an actual existing position with respect to a command position is larger than a prescribed value). PA1 c. Run-away of the NC controller 1. PA1 d. Electrical disconnection of the press encoder 12. PA1 a servo control means for controlling the induction type servo motor; PA1 means for detecting an occurrence of an abnormal condition of the servo control means and urgently stopping operations of a slide of a press body of the transfer press and the induction type servo motor; PA1 means for detecting a crank angle of the press body and discriminating an area in which the slide or a mold of the press body interfere with the transfer bar of the transfer feeder or an attachments therefor attached to the transfer bar; and PA1 means for driving the transfer bar to a position at which the slide and the mold of the press body do not interfere with the transfer bar of the transfer feeder and the attachments by applying an A.C. voltage to the induction type servo motor at a time when the operation of the slide and the induction type servo motor begin to be urgently stopped in the interference area. PA1 a servo control means for controlling the induction type servo motor, the servo control means comprising and NC controller for controlling a position of a transfer bar of a transfer feeder, a servo amplifier driven by a servo amplifier drive source and operatively connected to the NC controller for driving a motor of the transfer feeder for supplying an electric current to the motor, a brake power source for stopping the operation of the induction type servo motor at an occurrence of an abnormal condition of the NC controller or servo amplifier, and a selector operatively connected to the servo amplifier and the brake power source for switching an operation in accordance with a factor of the abnormal condition; PA1 means for detecting the abnormal condition of the NC controller or servo amplifier; PA1 a press encoder detecting a crank angle of the press body; PA1 a sequencer operatively connected to the NC controller for communicating an information therebetween and discriminating a fact whether a slide or mold of the press body and the transfer bar or the attachments therefor are within an area in which they are interfered with each other or not; and PA1 a further selector operatively connected to the first mentioned selector and the commercial power source for selecting a driving mode of the induction type servo motor, the further selector being operatively connected to the sequencer.
When such abnormal conditions occurs, the selector 5 is switched to the side of the brake power source 4, the D.C. voltage is applied to the induction type servo motor 7 for driving the transfer feeder 6, thereby urgently stopping the operation of the servo motor 7. At the same time, the slide of the press body is also urgently stopped. At this time, the sequencer 11 serves to memorize a fact that the abnormal condition occurs at what dimensional direction operation of the transfer feeder 6, and this abnormal condition is indicated to an operator through a display on the monitor, for example.
However, at the emergent operation stopping time, the transfer bar of the transfer feeder 6 and the slide or mold of the press body are independently stopped in their operations without synchronization thereamong, so that the transfer bar is first stopped and then the slide is stopped because of the difference in inertia magnitudes of the transfer bar and the slide and mold.
Because of such time lag for stopping the operations of the transfer bar of the transfer feeder 6 and the slide or mold of the press body, there may cause a case in which the slide or mold run away by the inertia interferes with the transfer bar or attachments mounted thereto, damaging the attachments or mold according to the stopped position of the transfer bar. Particularly, the mold is generally expensive, and accordingly, the damage of the mold may lead to the manufacturing cost increasing, and in addition, such time and labour will be required for the exchanging of the damaged mold with a new one, resulting in the lowering of the productivity of products, thus being also inconvenient.